Fire barrier



1967 K. G. FERREL E AL 3,

FIRE BARRIER Filed April 27, 1966 United States Patent 3,357,657 FIREBARRIER Kenneth G. Ferrel, Los Aiamitos, Charles 0. Gunderson, RollingHilts, and Raymond J. Palmer, Newport Beach, Calif., assiguors, by mesneassignments, to McDonnell Douglas Corporation, anta Monica, Calif, acorporation of Maryland Filed Apr. 27, 1%6, Ser. No. 545,638 8 Claims.(Cl. 244- 4) This invention relates to a fire barrier between anaircraft engine and primary structure on which it is mounted forpreventing serious damage from a burn-through flame. More specificallyan impregnated laminated cloth material is placed between the engine andfire wall for diffusing an engine burn-through flame as an aid todetection of flame and prevention of resulting damage.

Within an aircraft engine casing there are fuel lines and other highlycombustible elements which could cause serious fire if a small leakoccurs and the fluid escaping were to contact the hot components of theengine. Of course, there are many safety features that tend to preventsuch fire from becoming uncontrollable or invoking serious damage to theaircraft. Typically, engines are mounted on pylons which are attached tothe wings or fuselage of the aircraft and these pylons contain all theconductors of fluid, electrical current and other externally appliedelements necessary for the operation of the engine. For this reason, itis desirable that an effective fire wall be placed between the wing orfuselage and the engine.

There is another source of fire hazard, however, that is caused by afailure of the jet engine combustion chamber wall. An engine caseburn-through at the diffuser or burner section results in a highvelocity, torching flame of small diameter having a temperature as highas 3500 F. and a pressure of 125 p.s.i. at its origin. A flame of thistype directed through the attach structure is a potential danger. Thus,a special fire barrier is necessary, particularly in the area of theengine diffuser and the burner section where a burn-through flame wouldoccur. It also is desirable that such a fire barrier be of a lightweightmaterial that may be bolted on, so that it may be removed to provideready access to the other side of the barrier. Another desirable featureof a fire wall is that the fire barrier retain a flame at least untilthe detector elements nearby indicate a fire and permit remedial actionbefore serious damage occurs.

It has been found, in accordance with the present invention, that a firewall may be constructed which consists of a sheet of light-weight, heatresistant material, such as titanium, for example, and placing on thesurface thereof which would be subjected to the heat of an engine fire,a material that will form a barrier to disperse and deflect the flameback toward the engine. In this manner the heat ing of laterallydisplaced fire detector elements adjacent the fire wall is insuredbefore the burn-through flame cuts through the fire Wall.

It is therefore an object of the present invention to provide for a newand improved fire barrier material.

Another object is to provide for a fire wall of a lightweight removablematerial which will withstand an engine burn-through flame.

Another object is to provide for a fire wall between a fuselage or wingand an engine mounted therein or thereon which will prevent an engineburn-through flame from cutting through the fire wall by dispersing anddeflecting back said flame toward the engine.

Another object is the provision of a fire wall, between a fuselage orwing and an engine mounted thereon, which will disperse heat from aflame to laterally displace fire detector elements adjacent said firewall.

Other objects will become more apparent as a description of thisinvention proceeds, having reference to the drawings, wherein:

FIGURE 1 is a perspective view showing in phantom the relationshipbetween an engine casing, pylon, and fuselage in one embodiment,

FIGURE 2 is a sectional view taken along the line 2-2 in FIG. 1, showingthe deterents and dispersal of a burnthrough flame when the presentinvention is used,

FIGURE 3 is a perspective view of the pylon main box,

FIGURE 4 is a perspective view of the main pylon fire barrier, and

FIGURE 5 is a phantom sectional view of the fire barrier in anotherembodiment.

There have been several instances of burn-through of gas turbineengines. In a recent two-year period there have been reportedthirty-three failures and accordingly, the possibility of a majorincident has been of great concern to airplane manufacturers and airlineoperators for some time. The actual thermal protection of the pylon towhich the engine is mounted has not been satisfactory. For example, a3500 F. flame will penetrate a .025" titanium sheet in about twoseconds. The engine outer case and bypass airflow are the firstobstructions to such a flame. In general an engine fire wall is locatedsome distance from the engine case, possibly 18 to 20 inches. Themaximum flame temperature at the engine would be approximately 3500 F.but this temperature would be reduced to below 3000 F. at the fire wallbecause of the separation distance and the by-pass airflow coolingeffect. Accordingly, a temperature of 3000 F. was established as arealistic temperature that this fire wall must withstand.

A material has been found, in accordance with the present invention,which utilizes a multi-ply laminate of high silica glass, carbon orgraphite cloth impregnated with a ceramic filled organic resin systemsuch as a phenolic resin. This material is now available in two formsunder the trade names of Rezcoat, RF-192 or MXS- 6192 made by theFiberite Corporation in Los Angeles, Calif. After laminating and curing,the material resembles fiber glass board approximately ,5 thick. Whenthis barrier is bolted to the fire wall and subjected to a highintensity 3000 flame, it prevents burn-through for a duration of atleast fifteen minutes. With a 3500 flame the same material prevents aburn-through for three minutes. In contrast, when a bare titanium firewall is used, the burn-through occurs within twenty seconds with a 3000"flame and almost instantly with a 3500 flame.

A characteristic of an engine burn-through flame is that the flame ishighly concentrated and if directed on bare metal, a hole will developin the metal the size of the flame and very little heat deflection willoccur. A fire detector element only inches away from the flame probablywould not be heated sufliciently to cause the fire warning system tofunction. It has been found that with the fire barrier material of thepresent invention, the flame is dispersed and deflected back toward theengine to thus insure heating of fire detector elements in nearproximity to the flame. In order to insure protection of the fire wallagainst an engine burn-through flame, this fire barrier material isinstalled along the length of the fire wall adjacent to the diffuser andburner section.

Reference is now made to FIGURE 1 which shows in phantom a gas turbineengine housing 10 and pylon 12 connecting the engine housing to thefuselage of an aircraft by means of spars 14 and 16. This particularembodiment has the engines mounted near the tail of the aircraftadjacent the fuselage and is of the type popularly known as the DouglasDC-9. A sectional view taken along the line 2-2 of FIGURE 1 is shown inFIGURE 2. For purposes of simplicity, the internal structure of theengine is notshown but is represented by flame and gases 18. An engineburn-through may be caused by excessive heat, metal fatigue, or otherfactors which cause a rupture 20in the engine housing 10. The ruptureindicated by numeral .20 isin-a direction away from the pylon ,12 ,andaccord- ;ingly, does not present the :potentially dangerous conditionsuch as would be caused by a rupture 21in the direc- -tion .ofthe pylon.As previouslymentioned, a'fire barrier 24 is placed in such a positionthat it will disperse and deflect back a burn-through flame. This actionis represented by arrows .26 aud 28. The fnselage wall 30 in;this caserepresent-s a structure through which it would be highly undesirable fora burn-through flame to pass.

Amore detailed disclosure of the fire barrier for this embodimentisshown in IFLGURES 3 and 4- In FIGURE 3 there is shows a left pylon 12having a front spar,14 and -rear spar 1,6 for secure mounting of thepylon to the fuselage 30. The gas engine, not shown, ;is mounted on thepylon by forward engine mount yoke 32 and aft engine mount supports 34.Closing rib 36 has theinecessary :openings ,38 therein for the passageof necessary conductors, not shown, and to provide the bestpossiblestrength- -to-weight ratio. Adjacent the fuselage 30 is an inboard ribprimary fire wall .40, of fire resistant material such as titanium orstainless steel, against portions of which is positioned the firebarrier material 42 in accordance with the present invention.

The fire barrier comprising the present invention is shown ingreaterdetail inFIGURE 4. Here fire barrier 42 consists of a shield .44,cover 46, trough 48and shield 50, all having suitable openings andconfigurations to-permit its installation with a minimum of interferencewith other structural parts of the aircraft. Bolts or screws 52 permitremoval of the barrier 42 .for access to the other side, as desired.These bolts. or screws preferably are made ,of titanium or stainlesssteel -.which exhibits a high strength-to-weight ratio and have arelatively. high melting point. Outwardly from this shield and adjacentor in proximity thereto is the fire barrier material forming part of thepresent invention. This material may be laminated .-to the outer surfaceandaccordingly, can have the same config ration as the metallicstructure.

While the preferred embodiment shown in FIGURES .1 .through .4 is foundon an aircraft wherein the engines are mounted tothe side of thefuselage, this fire barrier has .ppplicationfln other types of aircraft.For example, in FIGURE 5, the engine housing 54 is suspended frompylon-5,6 attached to the lower surface of wing 58. The pylon has a firewall .60, under .which ismounted the engine burn-through fire barrier.62 which forms part of the present invention. This-barrier is in'linetoprotect against a burn-through flame from :the burner compartment:64.,A, .0wer engine fire detector loop '66 is in the compressor andaccessory compartment area .68 'whereas the upper-forward andaftpylon'fire detector loops 70, 72, are in the burner compartment area 74.Piping 76 carries a fire extinguishing :agent.

Itisto be :notedthat all embodiments of this inventionarecharacterizedxby the fire barrier material being placedbetweeuthe-burner section of the engine and the metallic fire wall sothat .a small hole will not be'burned thereis made.

It will be evident from the foregoing description that variousmodifications are possible and will readily occur to those skilled inthe art and it is to be understood that these variations are to beconsidered part of the present invention when within the scope oftheinvention as defined ;by the appended claims.

What isclaimed is:

1. In combination:

an aircraft having a support structure thereon,

an aircraft engine mounted on said support structure,

a fire wall mounted between said support structure and said engine forpreventing damage from an engine burn-throu gh flame,

said fire wall comprising a sheet of light-weight heat resistantmaterial and a fire barrier thereover,

said fire barrier comprising:

a laminate cloth material impregnated with an organic resin systemwhereby an engine burnthrough flame is dispersed and deflected backtoward the engine.

.2. The combination as set forth in claim -1 wherein said fire wall hasfire detector elements laterally displaced therefrom and said engineflame, when dispersed and deflected back, heats said elements.

3. The-combination as set forth in claim 1 wherein said firewall is inthe area of the engine diffuser and burner section.

.4. The combination as set forth in claim 1 wherein said laminate isfrom ,a class consisting of high silica glass cloth, carbon cloth andgraphite cloth impregnated with ;a phenolic resin.

5. The combination as set forth in claim 1 wherein said sheet istitanium.

6. The combination as set forthinclaim 1 wherein said glassclothismulti-ply lamiuatedof high silica and said phenolic resin is ceramicfilled.

7. The combination as set forth inclaim 1 whereby an engine burn-throughflame of up to 3000" E win require 15 minutes to burn through said firewall.

8. The Combination as set forth in claim 1 wherein said sheet isapproximately .032" thick, said laminate is approximately thick and bothare detachably mounted.

References Cited UNITED STATES PATENTS 2,9 68,920 l/1961 Wayneetal.-35.6

MILTON 'BUCI-ILER, Primary :Examiner.

B. BELKIN A isi!!! :Examiner,

1. IN COMBINATION: AN AIRCRAFT HAVING A SUPPORT STRUCTURE THEREON, ANAIRCRAFT ENGINE MOUNTED ON SAID SUPPORT STRUCTURE, A FIRE WALL MOUNTEDBETWEEN SAID SUPPORT STRUCTURE AND SAID ENGINE FOR PREVENTING DAMAGEFROM AN ENGINE BURN-THROUGH FLAME, SAID FIRE WALL COMPRISING A SHEET OFLIGHT-WEIGHT HEAT RESISTANT MATERIAL AND A FIRE BARRIER THEREOVER, SAIDFIRE BARRIER COMPRISING: A LAMINATE CLOTH MATERIAL INPREGNATED WITH ANORGANIC RESIN SYSTEM WHEREBY AN ENGINE BURNTHROUGH FLAME IS DISPERSEDAND DEFLECTED BACK TOWARD THE ENGINE.